This invention relates generally to blood vessel wall defining techniques and more specifically to a device and method capable of repairing aneurysms in large vessels employing percutaneous insertion.
Approximately 70% of the aneurysms reported in the United States each year are repaired by the conventional open surgical technique known as aneurysmectomy. However, the mortality rate associated with aneurysmectomy remains relatively high, 12.9% for elective surgery, 30-50% for emergency surgery after vascular rupture, and as high as 71% for patients over 70 years of age (Ruckley, In: The Cause and Management of Aneurysms, Greenhalgh R. M. et al. ed, W. B. Saunders, Philadelphia, p. 327-337, 1990; Lawrie et al, Surgery 85:483, 1979). Some of the factors involved in the high operative mortality rate are underlying coronary or cerebral atherosclerosis, severe obstructive pulmonary disease, and renal disease.
Another major disadvantage of aneurysmectomy is that, because of the nature of the operation, it can only be performed in medical facilities which have the sophisticated equipment necessary to perform major cardiovascular surgery. In cases where the prognosis for rupture is imminent, fatalities may occur because of insufficient time to perform diagnostic studies and/or transfer the patient to a major medical center where surgery can be performed. Therefore, there has been a long felt need for simpler, quicker and less traumatic techniques for repairing aneurysms.
Percutaneous techniques of blood vessel repair such as introducing vascular stents into arteries or veins have been suggested, and have had some significant applications, but known approaches have certain drawbacks and/or limitations and thus, have not found wide use with respect to large vessels, especially the abdominal aorta where a significant number of aneurysms occurs. Furthermore, it should also be borne in mind that the stents conventionally employed to open clogged arteries are quite different from an abdominal aneurysm stent, the latter often times has to deal with an aorta that is out of round cross-section wise because of the lesion area on the aorta.
Of late, the prior art workers have expended considerable efforts in the area of affecting repair of aneurysms of an abdominal aorta by specially fabricated stents. These efforts have led to the issuance of quite a few U.S. patents, namely:
U.S. Pat. No. 5,211,658 to Clouse
U.S. Pat. No. 5,360,443 to Barone et al
U.S. Pat. No. 5,387,235 to Chuter
U.S. Pat. No. 5,456,713 to Chuter
U.S. Pat. No. 5,522,880 to Barone et al
U.S. Pat. No. 5,562,726 to Chuter
U.S. Pat. No. 5,571,173 to Parodi
U.S. Pat. No. 5,676,697 to McDonald
U.S. Pat. No. 5,683,452 to Barone
U.S. Pat. No. 5,693,084 to Chuter
U.S. Pat. No. 5,755,777 to Chuter
U.S. Pat. No. 5,843,160 to Rhodes
The subject matter of these patents are incorporated herein by reference.
The present invention builds on the prior work of the instant inventor W. Henry Wall as exemplified in U.S. Pat. Nos. 5,192,307, 5,824,038 and 5,843,163. The prior material is incorporated herein.
The present invention provides a blood vessel wall-defining device; and a method for insertion of the wall-defining device within a blood vessel of an animal, preferably a human patient, which has an abnormal widening, or aneurysm, along a section of the vessel wall. The insertion is particularly applicable to aneurysms in an aorta, especially in the abdominal aorta below the confluence with the renal arteries and above the bifurcation of the aorta into the common iliac arteries.
According to a first aspect of the invention a blood vessel wall-defining device for repairing an aneurysm comprises in combination, a percutaneously-insertable structural frame extending between first and second ends having an unexpanded diameter which is smaller than the diameter of the blood vessel to allow the structural frame to be percutaneously placed into the blood vessel, the structural frame being expansible to form a generally cylindrical structural skeleton having a slightly larger diameter than the blood vessel to facilitate the securing of the structural skeleton in position in the blood vessel.
The structural frame includes a plurality of flexible elongated rods which are equidistantly affixed to a sheath of fabric constructed of a thermoplastic material such as nylon. The sheath has a tubular configuration. Prior to percutaneous placement, the tubular cylinder is in undistended accordian-like folds to present a diminished diameter. The rods may be constructed of a bio-compatible metal or plastic.
Internally of the sheath are a series of displaced ring stents of a thermoplastic material or a bio compatible metal having a memory. These ring stents are coiled upon themselves to present a smaller diameter which upon uncoiling will provide an enlarged annular configuration. The coiled ring stents are retained in a coiled-up condition by an elongated pin which upon successful placement is retracted to permit uncoiling of the ring stents. The uncoiling of the ring stents provide the mechanical means to unfold the sheath or tube of fabric material to which the flexible metal or plastic rods are equidistantly attached.
In one embodiment, the ring stents, when constructed of a metal having a memory, would ordinarily recoil except that the end portions are provided with a ratchet locking means that retains the ring stent in its uncoiled position and therewith resistant to re-coiling. The ratchet means may be of a selected number whereby the stent ring means may be opened and progressively held at various uncoiled positions but cannot revert to a coiled position. The ratchet locking means is similar to the one disclosed in said parent application Ser. No. 08/667,604, filed on Jun. 21, 1996.
Due to the fact the device is relatively long the stent may under ordinary circumstances cover openings to branch arteries. In such a circumstance, it has been found useful to have certain portions of the device devoid of the tube of fabric material or sheath whereby blood may easily pass through the spaces between the rods of the device of the present invention.
As stated in another way, the ring stent provides a direct impingement on the flexible metal or plastic rods, i.e. without the presence of the fabric material or sheath.
It is contemplated that the device of the present invention may be positioned not only in the abdominal aorta but also in smaller branch arteries. In such a situation the diameter of the resulting device may describe a smaller diameter. The device can have a tube of fabric material or sheath throughout.
In another embodiment, the device for percutaneous insertion is carried by a known type of balloon catheter in a folded condition. The ring stents are in a coiled-up condition which upon successful placement of the device of the present invention the balloon is then inflated. The pressure of the balloon internally of the ring stent uncoils the stent which in turn impinges on the rod carrying fabric tube or sheath thereby unfolding the sheath and spacing the rods appropriately. The rods and sheath are detailed to abut and define the vessel wall of the artery.